This invention generally relates to the art of electrical connectors and, particularly, to an electrical connector having ESD and EMI protection.
Electrical connectors are used in a wide variety of applications. Some connectors simply are used to transmit power from a power source to an appropriate appliance. Other electrical connectors are used to interconnect signal transmission lines to printed circuit boards, other electronic devices or to other complementary connectors. The transmission lines transmit signals through a plurality of conductors which, preferably, are physically separated and electromagnetically isolated along their length. Hybrid connectors are known in which both power and signals and/or data are transmitted through the connector interface.
Some electrical connectors also employ various types of shield structures, ground structures or the like to protect or to electrically interact with the transmission lines and their terminals within the connectors. For instance, some connectors are provided with shield structures to protect against electrostatic discharges (ESD) which are generated when the connector comes into contact with another conductive body which may be a complementary mating connector. In essence, the ESD shield is used to dissipate static charges.
Connectors also may have shield structures to protect against electromagnetic interference (EMI). In essence, the EMI shield protects the electrical circuitry from externally generated radiated emissions as well as preventing electromagnetic interference from radiating outwardly of the connector.
Typically, ESD and EMI shields are provided by stamped and formed conductive sheet metal components which conventionally surround the connector housing. The metal shield may be a one-piece structure or a multi-part structure with the multiple parts of the shield being in positive engagement. Such shielding structures often act as both an ESD shield as well as an EMI shield. In some instances, a pair of metal shields may be separated from each other by portions of the dielectric connector housing, but, in these instances, one of the shields is located substantially internally of the connector.
Heretofore, the fact that a one-piece shield or a multi-part shield acted both as an ESD shield as well as an EMI shield did not make much difference, because the connectors were provided primarily for signal transmission purposes. In other words, the dissipation of minor static charges did not cause any problem with grounding the EMI shield, even grounding the shield to a circuit board to which the connector is attached.
However, with the advent of what are called xe2x80x9ccomboxe2x80x9d electrical connectors, combined ESD and EMI shield have caused problems. A combo connector is an electrical connector which incorporates the combination of both signal transmission lines/terminals and power lines/terminals in the single connector. If the ESD shield and the EMI shield in a combo connector are commoned to each other or are grounded to a common source, such as a printed circuit board, an electrical discharge from one of the power lines/terminals could damage the printed circuit board or even overload the circuitry. There is a need for a simple grounding system to solve these problems, wherein the ESD ground means is electrically isolated from the EMI ground means for use in such electrical connectors as combination power and signal connectors, without the system being unduly complicated. Preferably, the system would involve the standard components of the electrical connector without requiring additional extraneous grounding apparatus. The present invention is directed to satisfying this need and solving the problems outlined above.
An object, therefore, of the invention is to provide an electrical connector with a new and improved shielding system wherein the ESD shield and the EMI shield are electrically isolated from each other.
In the exemplary embodiment of the invention, the electrical connector includes a dielectric housing having a forward mating end and a rearward end. A front ESD shield is disposed about the exterior of at least a substantial portion of the forward mating end of the dielectric housing. A rear EMI shield is disposed about the exterior of at least a substantial portion of the rearward end of the dielectric housing. The front ESD shield is electrically isolated from the rear EMI shield by an outwardly projecting portion of the dielectric housing physically separating the shields. Therefore, no extraneous insulating components whatsoever are required.
As disclosed herein, the forward mating end of the housing includes a receptacle portion for receiving a plug portion of a complementary mating connector. The front ESD shield is disposed about the receptacle portion, whereby the receptacle portion forms a dielectric barrier between the ESD shield and the plug portion of the complementary mating connector. As disclosed, the receptacle portion is generally rectangular, and the ESD shield includes a rectangular shroud surrounding the rectangular receptacle portion.
A feature of the invention is that the front ESD shield includes at least one retention portion for locking the shield to the outwardly projecting portion of the dielectric housing. In the preferred embodiment, the outwardly projecting portion is formed as a peripheral flange. The ESD shield includes at least one retention tab embracing the peripheral flange for fixing the ESD shield to the housing.
The invention is disclosed herein in a shielded electrical connector adapted for mounting on a printed circuit board and through an aperture in a conductive bracket. The front ESD shield is adapted for engaging the conductive bracket about the aperture therein. The rear EMI shield has ground means adapted for engaging a ground circuit on the printed circuit board.
The shielded electrical connector is adapted for mating with a complementary mating connector which includes a peripheral metal shield. Complementary interengaging latch means is provided between the peripheral shield of the mating connector and the dielectric housing of the shielded electrical connector. The complementary interengaging latch means includes a latch arm folded back from a forward end of the peripheral metal shield for engaging a latch member inside the forward mating end of the dielectric housing.